BUG/MINOR: log-format: fix %o flag

The %o flag was not working at all.
diff --git a/include/proto/log.h b/include/proto/log.h
index 66fbe34..43c84be 100644
--- a/include/proto/log.h
+++ b/include/proto/log.h
@@ -55,7 +55,7 @@
  * Parse a variable '%varname' or '%{args}varname' in logformat
  *
  */
-int parse_logformat_var(char *str, size_t len, struct proxy *curproxy);
+int parse_logformat_var(char *str, size_t len, struct proxy *curproxy, int *options);
 
 /*
  * add to the logformat linked list